AIR BAG Warning Lamp Circuit Malfunction

Circuit Description

The ignition switch supplies Ignition 1 voltage to the Inflatable Restraint Sensing and Diagnostic Module (SDM) at terminal A1 using the AIR BAG Fuse. The ignition switch also supplies Ignition 1 voltage to the instrument cluster. The AIR BAG warning lamp is controlled by the SDM via Class 2 serial data. When the ignition switch is first turned to the RUN position, the SDM responds by performing tests on the SIR system and then commanding the AIR BAG warning lamp OFF after it has flashed seven times. If IGNITION 1 is outside of the normal operating voltage range (9-16 volts), the AIR BAG warning lamp will come ON solid with no DTCs set.

Diagnostic Aids

The loss of serial data communication between the SDM and the instrument cluster will cause the AIR BAG warning lamp to come ON solid. Refer to A Diagnostic System Check. Diagnostic System Check

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

3. This step checks to see if the AIR BAG warning indicator flashes seven times when the ignition key is turned to the RUN position.

5. This step checks to see if the AIR BAG warning indicator is being commanded ON.

6. This step checks to see if the ignition voltage to the SDM is more than 9 V.

7. This step determines if the ignition voltage to the SDM is more than 16 V or if there is a malfunctioning SDM.

8. This step checks to see if the SDM wiring harness connector is corroded or damaged.

10. This step determines if there is an open or a high resistance in circuit 1139 or if there is a high resistance in the power feed circuit to the SIR Fuse.